The basic concept of a weapons barrier system that is suitable for airborne vehicles raises the problems of size, weight, and stowage. These are critical parameters for aircraft, and they generally oppose the design requirements of a physical barrier that is capable of stopping or defeating a high-explosive missile traveling at extreme velocities (in Vietnam, barriers made of steel chain-link fence were successfully used as a perimeter defense against RPG attacks). A further difficulty is presented by the need for any RPG barrier system to deploy in a very short timeframe (ideally on the order of 200-300 milliseconds).
Portable missile systems are a proliferating threat to aircraft, ground vehicles, and personnel. Authoritative studies such as the RAND Report (published by the RAND Corporation and available at www.rand.org) predict that this threat will increase as all types of missiles become more widely available. Heat-seeking missiles have been identified as a clear and present danger to both military and commercial aircraft. Rocket Propelled Grenades (RPGs) are one of the most deadly insurgent tools against helicopters and ground vehicles. Planned future use of tilt-rotor, hovering military aircraft will add yet another attractive target for these small and relatively inexpensive missiles. Studies indicate that available defense systems, such as IR flares that are simply dropped from an aircraft, are of marginal effectiveness against heat-seeking missiles. Technological advances, such as multi-spectral and filtered IR seekers used in heat-seeking missiles, are directed at further negating the effectiveness of simple dropped flare-type defenses. Laser-based defense systems have been proposed to deal with heat-seeking missiles, but they have not been proved effective to date and are not generally available. Some laser-based proposals are years away from practicality in terms of both technology and cost. Moreover, both laser and flare defense systems are completely ineffectual against both laser-designated and video-guided missiles. They are also useless against unguided threats, such as Rocket-Propelled Grenades (RPGS).